Department of Mechanical Engineering

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IIT Jodhpur

The application of High Strength Low Alloy (HSLA) steels has expanded to almost all fields viz. automobile industry, ship building, line pipe, pressure vessels, building construction, bridges, storage tanks. HSLA steels were developed primarily for the automotive industry to replace low-carbon steels in order to improve the strength-to-weight ratio and meet the need for higherstrength materials. Due to higher-strength and added excellent toughness and formability, demand for HSLA steel is increasing globally. With the increase of demand; other issues like the selection of filler grade and selection of suitable welding process for the joining of these steels have become very significant. This paper discusses the various issues regarding selection of suitable grade and selection of suitable welding process for joining of HSLA steels and issues concerning the structural integrity of HSLA steel welds.

World University root node

Advanced Materials Research

Issues in welding of HSLA steels

In the present work, the nonlinear response of a vertically moving viscoelastic beam subjected to a periodically varying contact load is investigated. The generalized Galerkin's method is used to discretize the nonlinear partial differential equation of motion into the temporal equation of motion. The temporal equation of motion contains many nonlinear terms such as cubic geometric and inertial nonlinear terms, nonlinear damping term, and nonlinear parametric excitation terms in addition to forced excitation and parametric excitation terms. The first-order approximate solutions are obtained by using the method of multiple scales, and the stability and bifurcations of the obtained steady-state responses are studied. Extensive numerical simulations are presented to illustrate the influences of various types of system parameters for different resonance conditions. A significant amount of vibration reduction is obtained with the increase in the material loss factor. The results obtained by numerically solving the temporal equation of motion are found to be in good agreement with the results determined by the method of multiple scales. The obtained results are useful for reduction in the vibration of the viscoelastic flexible beam with prismatic joint or single-link viscoelastic Cartesian manipulator with payload subjected to a sinusoidally varying contact load. © 2010 Springer-Verlag.

Acta Mechanica

Nonlinear response of a vertically moving viscoelastic beam subjected to a fluctuating contact load

Identification of defects on highly reflective coated ring components using dark field illumination and image segmentation using simple thresholding technique

We present planforms of line plumes formed on horizontal surfaces in turbulent convection, along with the length of line plumes measured from these planforms, in a six decade range of Rayleigh numbers (105 &lt; Ra &lt; 1011) and at three Prandtl numbers (Pr = 0.7, 5.2, 602). Using geometric constraints on the relations for the mean plume spacings, we obtain expressions for the total length of near-wall plumes on horizontal surfaces in turbulent convection. The plume length per unit area (Lp/A), made dimensionless by the near-wall length scale in turbulent convection (Z w), remains constant for a given fluid. The Nusselt number is shown to be directly proportional to Lp H/A for a given fluid layer of height H. The increase in Pr has a weak influence in decreasing Lp/A. These expressions match the measurements, thereby showing that the assumption of laminar natural convection boundary layers in turbulent convection is consistent with the observed total length of line plumes. We then show that similar relationships are obtained based on the assumption that the line plumes are the outcome of the instability of laminar natural convection boundary layers on the horizontal surfaces. © 2011 Cambridge University Press.

Journal of Fluid Mechanics

Length of near-wall plumes in turbulent convection

Robotics has emerged as a major field of research and application over the years, and has also found a place in the curriculum of universities. Robotics as a course is challenging both for the teachers to teach and the students to learn as it involves 3D transformations, algebraic and differential equations, etc., which are difficult to understand. Several robotics learning software have been developed have helped to ease the learning of robotics as a subject. A similar attempt was made in developing RoboAnalyzer, a 3D model based robotics learning software that modelled a serial robot based on its DH-parameters. It could perform forward kinematics and show animation and graph plot as outputs. In this paper, further development of RoboAnalyzer is reported in the form of addition of inverse and forward dynamics analyses of a generic serial manipulator. The important contributions of this paper lie in the development of algorithms using an object oriented modelling approach and the Decoupled Natural Orthogonal Complement (DeNOC)-based recursive formulation. A KUKA KR5 robot was modelled in the proposed software, and the results were verified with those obtained using the Dynamic Simulation module of Autodesk Inventor. RoboAnalyzer can be downloaded for free from http://www.roboanalyzer.com and can be used almost instantly.

15th National Conference on Machines and Mechanisms, NaCoMM 2011

Recursive robot dynamics in RoboAnalyzer

In this work, the nonlinear vibration of a cantilever beam with end mass subjected to both static and alternating transverse magnetic field has been studied. The governing temporal equation of motion of the system which contains nonlinearities of geometric and inertial type along with parametric excitation and non-linear damping terms due to the body force and couple generated by the magnetic field has been derived. Method of multiple scales (MMS) is used to determine the instability region and frequency response curves of the system. The influences of the damping, amplitude of static and dynamic magnetic field strength, and tip mass on the instability regions and frequency response curves for simple and principal parametric resonance conditions have been investigated. These results are found to be in good agreement with those obtained by numerically solving the temporal equation of motion. © The Author(s) 2010.

JVC/Journal of Vibration and Control

Nonlinear response of a soft magneto elastic cantilever beam with end mass under static and dynamics magnetic field

The non-linear response of a magneto-elastic translating beam having prismatic joint for higher resonance conditions is studied. A periodically varying transverse magnetic field is applied to the system. Two frequencies of prismatic motion and oscillating transverse magnetic field are implemented to the system. The method of multiple scales as one of the perturbation techniques is used to derive two first order ordinary differential equations that govern the time variation of the amplitude and phase of the response. Then a stability analysis is conducted for subharmonic resonance and simultaneous resonance conditions. A parametric study is performed to investigate the effect of magnetic field strength, amplitude of prismatic motion, damping and payload mass on the frequency response curves for both the resonance conditions. The catastrophic failure of the system may occur due to the presence of saddle-node and pitchfork bifurcations. The results obtained by method of multiple scales are compared with those obtained by numerically integrating the reduced equations and are found to be in good agreement. The developed results can be applied to control the vibration of a beam with prismatic joint subjected to magnetic field for third order subharmonic resonance and simultaneous resonance conditions. © 2011 Elsevier Ltd. All rights reserved.

International Journal of Non-Linear Mechanics

Non-linear response of a magneto-elastic translating beam with prismatic joint for higher resonance conditions

A generalized enthalpy update scheme is presented for evaluating solid and liquid fractions during the solidification of binary alloys, taking solid movement into consideration. A fixed-grid, enthalpy-based method is developed such that the scheme accounts for equilibrium as well as for nonequilibrium solidification phenomena, along with solid phase movement. The effect of solid movement on the solidification interface shape and macrosegregation is highlighted. © The Minerals, Metals & Materials Society and ASM International 2011.

Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science

Communication a generalized enthalpy update scheme for solidification of a binary alloy with solid phase movement

In this paper, nonlinear vibration of a cantilever beam with tip mass subjected to periodically varying axial load and magnetic field has been studied. The temporal equation of motion of the system containing linear and nonlinear parametric excitation terms along with nonlinear damping, geometric and inertial types of nonlinear terms has been derived and solved using method of multiple scales. The stability and bifurcation analysis for three different resonance conditions were investigated. The numerical results demonstrate that while in simple resonance case with increase in magnetic field strength, the system becomes unstable, in principal parametric or simultaneous resonance cases, the vibration can be reduced significantly by increasing the magnetic field strength. The present work will be very useful for feed forward vibration control of magnetoelastic beams which are used nowadays in many industrial applications. Copyright © Taylor & Francis Group, LLC.